1. Field of the Invention
The present invention relates to multi-dimensional modeling of solids in computer aided design and computer aided manufacturing systems. More particularly, the present invention relates to a sketching system that facilitates creation and manipulation of planar geometries within a three-dimensional workspace.
2. Discussion of the Related Art
In a typical computer aided design/computer aided manufacturing (CAD/CAM) system, a user interacts with the system to design a model that can later be used to manufacture a product according to the specifications of the model. During the design process, the user creates or sketches parts of the model on the computer system's display using various two-dimensional geometric primitives such as lines, arcs, circles, slots, rectangles, etc. that interact to form geometries that define the model being designed. Because such a model is typically used to manufacture a product that has three dimensions, a CAD/CAM system typically provides a capability for the user to enter and manipulate data that defines a three-dimensional model. However, most display devices typically used in CAD/CAM systems are inherently two-dimensional. As a result, special provisions and capabilities have been developed for CAD/CAM systems to facilitate the development and use of three-dimensional models, such as the ability to rotate the user's two-dimensional view through three-dimensional space while representing the designed model with accurate aspect views and size relationships.
One approach to allowing a user to design aspects of a three-dimensional model is to provide a sketcher on which the user can quickly yet accurately create geometric primitives and objects in two dimensions (referred to as planar geometry). The user can then map the planar geometry formed on the sketcher into three-dimensional space at a desired location, desired orientation, and depth to have the desired effect on the three-dimensional model. An example of a desired effect on a three-dimensional model is to bore a hole through part the model, the hole being represented by an extrusion of a geometry (e.g., a circle) from the sketcher. However, because the sketcher operates in two dimensions, it is often difficult for the user to visualize the effects of his two-dimensional sketching on the three-dimensional model, prior to the time at which the user maps the resulting planar geometry onto the three-dimensional model. Thus, it would be desirable to provide a facility by which a user operating a two-dimensional sketcher can concurrently view the results of the sketching operations in a three-dimensional work space that contains the three-dimensional geometry to which the sketched geometry will be mapped.
Additionally, because the user is working in a two-dimensional plane within the sketcher, it would be desirable to provide the capability for the user to designate elements of the planar geometry which are positioned relative to a point of interest within the three-dimensional space on an existing three-dimensional geometry, or to have other relationships to such a point of interest.